12 Mr. H. J. Carter on three Pachytragous Sponges 



General Observations. 



The cliief point of interest, perhaps, in the foregoing descrip- 

 tions is the presence of the peculiar cells mentioned in Der- 

 citus niger and Stelletta aspera^ corresponding in multiplicity, 

 position, and general distribution, though not in comjjosition, 

 to the globular crystalloids or little siliceous balls in the crust 

 and body of the Geodida?; add to this their contents, which 

 render them so much like reproductive agents, and, lastly, 

 their occurrence in the two sponges mentioned, and not at all 

 in the third, viz. Stelletta lactea. Nor do they exist in Pachy- 

 matisma Johnstonia ; but in the dried specimens of Geodia 

 gigcis^ presented to the British ^luseum by Dr. Oscar Schmidt, 

 there are similar cells in abundance, together with the globular 

 crystalloids. 



Although analogous in multiplicity, position, and distribu- 

 tion to the globular crystalloids in the Geodida3, they not only 

 differ from them, as just stated, in composition, by the former 

 being cellular and albuminous, while the latter are solid and 

 siliceous throughout (Annals, 1869, vol. iv. p. 16 &c., pis. 1 

 & 2. figs. 12 & 14), but also in size; for the largest crystal- 

 loids are three or four times as large as the largest cells, and 

 the latter much larger than the smallest or youngest crystal- 

 loids, so that in these respects, viz. in composition and size, 

 they cannot be confounded. 



Formerly I thought that the colour of the sponges might be 

 always sought for in the ampullaceous sacs (" Wimperkorbe," 

 Schdt.), and therefore that the black cells oi Dercitus niger 

 might be ampullaceous sacs (Annals, 1870, vol. vi. p. 332) ; 

 but the result of more particular examination subsequently, as 

 given above, has caused me now to regard the latter more as 

 reproductive agents. 



I have also alluded (Annals, I. c.) to the presence of ampul- 

 laceous sacs in Geodia gigas, Schdt. ; but on examining these 

 also again, now that I have become more intimately acquainted 

 with the composition of the cells in Dercitiis niger &c., I am 

 led to conjecture that they also may be of the same kind as the 

 latter, in which case, should I be right, we shall have an 

 instance in this sponge where both the globular crystalloids 

 and the cells occur together, and thence have to seek for the 

 ampullaceous sac under some other forai than that in Hali- 

 chondria simidans (see Annals, I. c), not only in Geodia gigas^ 

 but in Pacliymatisma Johnstonia and in Stelletta lactea &c., 

 where there is nothing of the kind like the ampullaceous sac 

 of the Halichondria mentioned, so far as the larger size of its 

 cellules and peculiar grouping go. The ampullaceous sac with 



